The present invention relates to biomass fueled stoves and boilers and, in particular, to a high efficiency wood or other biomass fueled stove/boiler wherein multiple combustion chambers and exhaust gas conduits are collectively surrounded by a liquid thermal transfer chamber to capture released heat energy and wherein exhaust gases to repetitively subjected to turbulent, pre-heated, pressurized combustion air to burn off hydrocarbons and other pollutants.
A wide variety of low-pressure wood and alternative biomass fuel (e.g. wood, coal, corn and other seeds, chips, pellets, crop waste etc.) stoves and boilers have been developed for residential and commercial use. Many of the boiler assemblies are constructed as stand-alone, weatherproof assemblies that are remotely located adjacent a heated building. Low pressure liquid supply lines are conducted from the boiler to an insulated, liquid distribution system at the heated facility. The heated facility is thereby isolated from any fire danger and exhaust gases are dispersed to the environment.
Many existing wood fueled stoves and boilers are relatively inefficient and exhaust smoke and flue gases that contain high concentrations of hydrocarbons that are hazardous to the environment. Efforts increasingly have been extended to improve stove/boiler efficiencies to increase thermal capture and reduce carbon emissions.
The present invention and novel biomass fueled stove/boiler was developed to provide a stove/boiler that is compatible with wood, coat, pellets and other biomass materials and is capable of burning the organic biomass fuel materials at efficiencies in excess of 90% with substantially reduced hydrocarbon emissions. The stove/boiler includes refractory lined burn chambers and a surrounding liquid thermal transfer chamber. The thermal transfer chamber and other heated surfaces are covered with sprayed urethane foam insulation to assure optimal heat transfer.
Preheated, pressurized combustion air is supplied to a primary burn chamber via surrounding horizontal and vertical orifice containing conduits. Exhaust gases are substantially directed via positive or negative fan directed pressurization into a lower, secondary burn/ash collection chamber via a secondary burner supplied with preheated, pressurized secondary combustion air. The secondary burner directs preheated pressurized combustion air into a shaped combustion space to produce turbulence and enhance combustion of hydrocarbons and pollutants.
The secondary exhaust gases are directed from the secondary burn/ash chamber via several fluted, fire or exhaust tubes that extend at acute angles through the liquid thermal transfer chamber to a further heated mixing chamber before being exhausted from an insulated stove flue. The wall geometry and cross-sectional shape of the fire tubes promote internal turbulence and heat transfer. The tubes can be straight or can include appropriate bends. The shaping and angular extension of the exhaust tubes promotes optimal heat energy collection, hydrocarbon combustion and carbon ash collection.
One or more tertiary fuel burners (e.g. oil or gas (natural or propane)) can be fitted to the primary burn chamber, between the primary and secondary burn chambers or at the secondary burn chamber. The tertiary burners can sustain exhaust gas combustion, facilitate cold starts or operate to adjust for changing fuel supply costs and availability.
An associated stove controller operates and/or responds to a combustion air source, airflow baffles, liquid supply and return pumps, sensors, switches and servos in conjunction with sundry operating sensors to accommodate several operating modes. The sensors monitor relevant operating parameters to optimize safety and burner efficiency and minimize back drafts.